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2 of my tropical fish - mollys- have some fin rot. One has

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2 of my tropical fish - mollys- have some fin rot. One has lost most of it's top fin, the other has sections missing from tail fin plus it has kinda stuck together - not like the other fish.

Does this sound like fin rot? They have a faint white film also

What shall I treat them with - I am in the UK so antibiotic food is not freely available. My friend is a vet and can get me metronidazole - I can get some tonight.
he said I could try a 1 litre bath using 10ml of the treatment for 1 hour - reapeat daily for 7 days - will this work?

Does it sound like fin rot or could it be soemthing else? He was also talking about injections....My wife can do this as she is a Medical Doctor, but need to know it will work. An that I have diagnosed the diesease correctly. 2 fish dies 2 weeks ago with absolutely no symptoms at all.
The water quality is good, no ammonia, no nitrite, under 10ppm Nitrate. I have had this tank 8 months no issues. No new fish bought although population increased breeding..



From what you have described this definitely is a case of Fin Rot which is a bacterial disease accompanied by a fungus (faint white film).


Administering metronidazole would not be the appropriate medicine to use as it is designed to treat parasites but not bacterial issues.


What I recommend be done is start off by changing 25% of the water in the tank.

Right after doing the partial water change add some aquarium salt at a ratio of 1 tablespoon per every 20 litres of water. Aquarium salt helps the healing process, serves as a general tonic and helps prevent secondary infections from occuring.


There's a medicine I'd recommend that's readily available in The UK and it's called

Interpet No 9 Anti-Bacterial Treatment which is designed to treat both Fin Rot and fungus. If possible try and obtain this product and treat the fish with it. Follow tthe directions on the product label for usage/dosage instructions.


If you encounter difficulty in finding the Interpet medicine and can have your wife obtain a substitute medicine then you can use the generic medicine erythromycin but I'm a bit unsure as to the proper dosage amount with the medicine in pure/raw form.


As for an underlying cause. Usually unfavorable water conditions are the culprit but as you have noted that ammonia/nitrites=-0- and nitrates 10ppm or lower this is obviously not the case. No new fish were added so this precludes a new addition bringing a disease into the tank.


So I would check the water temperature which should be in a steady range of 24c-26c degrees and the ph which should not fluctuate and be in a range of 7.0-7.4.

Now please keep in mind I'm assuming there's no goldfish present in the tank otherwise things change a bit.


Best wishes and please let me know if you have any questions.



Customer: replied 7 years ago.
Hi thanks for getting back.

There are no goldfish in the tank. There are approx 12 Lemon Tetras and what started off as 10 mollies/platties - this has increased as they have bred like crazy - there are now 10 adults and 5 young and 7 babies....The tank is 100 litres so I'm sure it's not overstocked. My heater was playing up recently and the temp dropped to 22 this would not help.

So it is fin brother tried this interpet no.9, years ago when he had a goldfish with similar symptoms but it did not work...and died after a week so I am a bit sceptical!!

I will try it of course. Shall I treat the whole tank or just these 2 fish as daily baths? What are your thoughts on the Natural Tea Tree remidies?

I could get some antibotics from my vet friend - would this be better than the interpet? Also should I do salt baths of the effected fish? If so what is the dosage please? I have a carton of aquarium salt so I can treat the tank right away but do I just add it in or slowly over a few days?

Finally I have many plants in there and notice lots of dead leaves I am always cleaning out....could this be the underlying problem? And there is green algea inside....I don't think I'm overfeeding but maybe I am - how much should I put in?

I know there is lots more questions here so I don't mind paying you a bit more for your time!

Many Thanks,


If possible try and seperate the affected fish in a quarantine/hospital tank.


I would not recommend treating the fish with baths. It would be better to have the aquarium salt present in the tank with the medicine so they would be exposed to the salt and medicine for the whole time they're being treated. This way they'll get the full effect.


I've also found baths to be a bit risky as the principal behind them is to expose the fish to a higher than normal dosage amount of salt/medicine for a brief period of time. This often backfires with the fish going into shock and subsequent death.


Do not add any type of salt to the tank where tetras are present as they do not take kindly to salt which is why it's better to treat the fish in a seperate tank.


If you feel uncomfortable using the Interpet medicine then as I suggested earlier you can try the generic tetracycline although I've generally heard good reports from my fellow fishkeepers across the big pond re: their experiences with the Interpet medicine in question and other Interpet products.


As for the natural tea tree remedies which are sold under the names of Melafix and Pimafix, I find them to be lacking in sufficient strength/potency to effect a cure in many cases especially advanced cases of bacterial disease. It won't hurt to try one of them but they should not be administered in conjunction with other medicines.


The dead leaves you are seeing are not necessarily a bad indication. It's possible that the water quality doesn't support the particular type of plant(s) you have in the tank thus the excess die-off of leaves. Plants can be fussy little creatures.


Alage is an indication of overfeeding and overlighting (too much light). I'm surprised that with plants present in the tank you'd have algae as plants compete for the same nutrients as algae.


Best to feed the fish 1 small pinch of food once a day. Please note that a fish's stomach is the size of one of its eyes.


Jim, don't worry about the money/payment. Ask as many questions as you like.





Customer: replied 7 years ago.
Ahh thanks...

...Looking at the interpet range they do a seperate one for fine rot and this no.9 for internal bacteria......which one do I use?

Also I got it wrong, not lemon teras at all (bit tired not thinking straight!!) they are infact glowlight tetras so I take it the same applies? no salt?

I do not have a seperate tank that I can use - I don't have a filter / heater spare - I suppose I could buy a cheap hospital tank tomorrow?....what size should I get and also it will not be cycled so what do I do about this?

Many Thanks!

Either Interpet product should be fine but try and use the Fin Rot one preferably.


Lemon tetras, glowlight tetras--not important--absolutely no salt for tetras and no hard water or high ph's. With Mollies it's the reverse, salt--either aquarium or sea=fine, hard water a plus and higher ph's preferred.


As for a quarantine tank--nothing elaborate. An 8-10 litre tank with an air stone and small heater is sufficient. Something basic to cover the tank is helpful so as to prevent jumping. In an emergency a plastic bucket will do. So as to avoid cycling issues you can fill the tank with 3/4 water from the main tank and 1/4 new fresh dechlorinated water.


One more thing Jim. I know you've mentioned that the water was tested but as a precaution keep testing every few days. You know the proper test results--ammonia/nitrite=-0- and nitrates 20ppm or lower.





TROPICAL FISH AFICIONADO and 2 other Pet Specialists are ready to help you
Customer: replied 7 years ago.
many thanks! will let you know how I get on....I think if I can still contact you after I accept!


and have a great christmas.

You're most welcome Jimmy. The pleasure's been all mine.


Yes, please do keep in touch. You can continue on this same post.


Warm regards XXXXX XXXXX a very Merry Christmas! and thank you for your accept and kind feedback.





Customer: replied 7 years ago.

ok one further question for ya...

Interpet no.8 cures fungus and finrot / mouthrot bacteria Myxobacteria sp. and Flexibacter sp.


Interpet no.9 cures infections caused by Pseudomonas, Aeromonas & Vibrio bacteria.

Which one is more appropriate please?



Use #8.



Customer: replied 7 years ago.

Happy xmas...

I now have a 20 L hospital tank with filter (some media from main tank) heater ....used 3/4 old tank water and 1/4 in there with salt and started on WaterLife fin-rot treatment MYXAZIN as aquatic centre said it was a more successfull tretament than the interpet....they also said try and brush effect area - but not sure how to do this - any ideas?

I am feeding small amounts....

...found out main tank might be close to max stocking levels due to the platties breeding so much plus I think I was overfeeding..... back to the turkey!!!

Have a great day,


Hey Jimmy and a Merry Xmas to you.!


Good move getting the 20L hospital tank. You set it up excellently.

The Myxazin is fine to use for this situation.


As for brushing the affected area. Jimmy, I'm one of those fishkeepers who is an advocate of a hands-off approach to fish. My reasoning for this is that a fish's exterior contains something called a slime coat which is basically the fish's first line of defense against disease. If when performing a hands-on procedure with the fish, something is not done right then there could be serious consequences. Basically when handling fish there's no room for error.


But if you feel comfortable in attempting to brush the affected area I'll share with you the best way to do it. Apply some of the medicine to a Q-tip and ever so slightly apply the Q-Tip to the affected area on the fish. Try and make sure the Q-Tip is completely moistened before using on the fish. Remember that this must be done quickly and with a light touch so as to not stress the fish too much.


Enjoy the turkey!



Customer: replied 7 years ago.
Hi again,

One more quick question.....should I be doing water chnages each day during treatment to keep water quality perfect?

I won't use the brush risky.


It's best to follow the directions on the medicine's product label with regards XXXXX XXXXX changes as some medicines recommend a partial water change every 3 days, some at different intervals.


Also check to see if the product label suggests removing any carbon media, that might be present in the filter, during treatment.



Customer: replied 7 years ago.

doesnt mention water changes at does say to remove carbon which I have. It's just that the water in the hospital tank has gone very slightly cloudy and I wanted to put some fresh in there.........

Label Says: use on days 1234 & 5. 1 drop per litre.

What do you think?


What I would do is before starting treatment change 50% of the water. The cloudy water represents a bacterial bloom which is normal but we don't need it occuring now.


As there are no instructions re: water changes I'd say change 50% of the water every 3 days. What we do not want to happen is have lethal ammonia form. If at any time the water gets cloudy do a 50% water change.



Customer: replied 7 years ago.

When I set the tank up I used 3/4 main water tank and 1/4 fresh (like you instructed).

I also put a small piece of filter media from the main tanks filter, in the new filter to aid the goodbacteria establishing here.

I am now on day 3 of the signs of change in the fish....but they ARE still alive.

If I take water away that has been treated will I be taking the medicine out of the water also or does it only last 24hrs each dose that is why you administer each day (or is it a slow build up that treats the fish)...

...Sorry for all the've well & truly earned your £7!!!


Yes when a partial water change is done it will lessen the potency/strength of the medicine which is why when doing partial water changes it would be a good idea to add the corresponding amount of medicine to the water being added.



Customer: replied 7 years ago.
Hi again,

Things have got a lot worse.

Both the fish died.

Then 4 days ago a glowlight tetra started darting about erratically. He had trouble swimming, could keep straight listing to one side. I put him in a hospital tank (cleaned since other two died) and treated him with Interpet no. 8 anti fin rot & fungus.. He is getting worse, not moving much on his side in bottom of the tank. Breathing quickly...not eating, small trailing white poos, fin erosion.

Now in the main tank a platy has a white cotton wool type growth and starting of fin erosion, I think this is an outbreak of Flexibacter Columnaris???

I immediatly did a 30% water change and treated main tank with Interpet No.8.

I recently found out that my tank is not overstocked, but underfilteres. I have a fluval 3....and now have just ordered a Fluval U4, much bigger.

What can i do to help the remaining fish? I have to wait a week untill I can re-dose any meds.


Sorry to here about the deaths.


Have you tested the water for levels of ammonia, nitrites and nitrates and if so what were the exact results? This is always the first place to look.



Customer: replied 7 years ago.
Yes I have had a Nitrite spike of 0.1ppm for some reason??? Other readings are pH8, Nitrate .10ppm, Ammonia 0ppm, 25c.

I have added redmoor wood decor and some live plants plus some fertiliser for the plants...these are the only changes.

I actually destocked the tank 2 weeks ago to the local fish shop so now only have 5 glowlighs and 8 platys, then bought x2 honey gouramies....they are ok......

But this morning a large platy has the slight cotton wool type growth round his mouth and fins starting to erode with more of this cotton wool stuff - that is what makes me thinbk it is Flexibacter Columnaris - it looks the same as the various images I have seen on google.

What shall i do? Why am I getting these issues? I'm hoping changing the filter is gonna help this situation.

Is the interpet no.8 the right meds to use for both the main tank and the smaller tank?


I suspected a water quality problem because there appears to be a chronic disease issue in the tank.


Jimmy, before any action can be taken nitrites need to be eliminated as they will offset the benefits of any treatment plan.


Do a 30% partial water change and drastically reduce feedings for now.


Once nitrites test at -0- and if ammonia remains at -0- can you go to the next step.



Edited by TROPICAL FISH AFICIONADO on 1/29/2010 at 10:08 PM EST
Customer: replied 7 years ago.
Ok - I did a 30% water change today.

Then I treated with the interpet no. 8.

What do I do now?

Maybe I might be overfeeding. How much food should I use for this many fish?
Customer: replied 7 years ago.
I'm thinking of just using this:

If I do what about the meds in the tanks already - shall I just change all the water then do this as above in instructions?

The bacteria is obviously in my tank to stay.....this I think will wipe it all out for good???

It says I can keep filter media safe whilst doing this?

Please help!

Jimmy as I mentioned earlier in order for a treatment/medicine to be successful the nitrites in the water have to be eliminated. I truly understand your frustration and desire to quickly deal with the disease(s) but with either ammonia and/or nitrite present in the water no medicine will work. It's that simple.


It's important that you comprehend the ramifications of tank water that contains nitrites.

Listed below is a link, click on it, which will supply you with some fundamental information re: nitrites.


Another possible drawback to adding medicines whilst there is nitrite in the water is that some, not all, medicines will kill the beneficial bacteria needed to consume nitrites!


You wrote-"The bacteria is obviously in my tank to stay.....this I think will wipe it all out for good???". If you're referring to nitrites this is not true. With the appropriate measures taken and some patience nitrites can be eliminated but if the proper stimulus is present in the water then nitrites will indeed form and wreck havoc as you have witnessed.


You also wrote-"Maybe I might be overfeeding. How much food should I use for this many fish?" Most likely you were/are overfeeding and overfeeding is definitely a stimulus for nitrite formation. For now feed the fish only a small pinch of food once every other day. When the water parameters return to normal you can then feed the fish a small pinch of food once a day.


Now as an option what you can do is seperate a few/one of the sick fish into a smaller quarantine tank using all new dechlorinated water. This water will obviously be ammonia/nitrite free thus providing the foundation for proper treatment.


It is in this tank that you can administer the medicine that corresponds to the particular illness you are treating for but remember that in order to not let ammonia/nitrite form you will need to do 50% partial water changes every other day in the quarantine tank.


Keep in mind that you must keep a fish(es) in the main tank because if all the fish are removed from it the whole biological balance will collapse and you'll need to start all over

again and if you think 0.1ppm nitrite is problematic you haven't seen nitrite levels in a newly set-up tank (tank with all new water)--.4ppm-.6ppm!


Ok-- as for the medicine JBL Furanol, it's ideal for use in treating a wide variety of bacterial aiments.






Customer: replied 7 years ago.

I think the issue is underfiltration and feeding too a better filter has been ordered - here next week....and I'll cut down on the food.

I see what you are saying. My main tank had 0.1ppm nitrite, then I did 30% water change and then used interpet no.8. It says to leave for one week. But if I start taking water out and doing water changes then the meds will go out too. So what am I to do here??

Also I can't move the fish with the problems out of this tank as my hospital tank has the glowlight with swim bladder issue....being treated with that medication.

The JBL is seen as a real last resort here - it wipes out all bacteria, including filter bacteria - and suggests saving filter media in a damp cloth untill treatment ended then replace and add filter replenish bacteria / cycle to boost the filter again.....but again because I treated main tank wI ith the interpet, can't do this without massive water changes....or wait a week.

So I guess what I'm saying is shall I see if the interpet no.8 will work before trying the JBL?


Do i do water changes every other day - how much? and what about the meds that will be coming out of the tank?


I agree about the underfiltration and overfeeding being the most likely causes of the problem as they usually are.


Yes do a water change and don't worry about the medicine in the main tank because as I stressed earlier the medicine is not going to do any good until nitrites are eliminated.

Jimmy---forget about the meds until the water is good.


The JBL if used should be used in a seperate quarantine tank. This is actually good procedure for treatment with most medicines.


Do small (10%) partial water changes every other day in conjunction with reduced feedings in the main tank so as to eliminate nitrites. Jimmy I think this should get better fairly quickly as we're not talking about a skyrocketing level of nitrite thank goodness.


To simplify things for now and for the future--only administer medicines in the quarantine tank. This seperate tank is going to become the hospital tank.

Basically if a fish gets taken ill in the main tank it should be whisked to the hospital tank for treatment. This method of doing things will prevent medicines from throwing off the biological balance in the main tank.



Customer: replied 7 years ago.
ok cool....just did another test 0 ppm ammonia, UNDER 0.1ppm Nitrite (some colour - still not zero), UNDER 0.5ppm Nitrate, pH8.

So it is going down with that water change. So will the fish that has Flexibacter Columnaris in the main tank heal if the water is improved? And if I do more water changes in this tank do I put back in more meds or forget that for now?

The other chappie in the hospital tank is still alive.....still on his side though.....I will keep this water prestine and hope for the I feed / try feeding him?

Thanks for all the help....bonus on it's way soon!


Great!--the water's making progress. Like I mentioned earlier--we're not talking about a heckuva lot of nitrite to get rid of.


Although the water is improving the fish with Columnaris will need treatment but remember in the hospital tank not in the main tank. I know you mentioned that the hospital tank has another patient in it but I don't think treating for columnaris will negatively affect the current inhabitant of the hospital tank.


Keep in mind Jim---good water quality will not heal a sick fish but unfavorable water quality will accelerate a fish's decline when it's sick. Also--constant good water conditions will almost always prevent disease from occuring.


Do a 10% partial water change in the main tank within the next 24 hours. I think by perhaps late Sunday the nitrite will have disappeared.


You can try feeding the fish in the hospital a very small pinch of food to see if it accepts it.


My goal here is for you to have the main tank with optimal water quality which means--and here goes my famously repeated phrase--- -0- ammonia . nitrites and nitrates 20 ppm or lower. Jimmy I stress this not to be a nag but because water quality is so vital to fish.

Think of having ammonia and nitrite laden water passing through the gills of a fish as us

(humans) having a high dosage of carbon monoxide passing through our lungs on a

continuous basis--certainly not healthy and almost certainly deadly.







Customer: replied 7 years ago.
ok thanks, XXXXX XXXXX you updated!


Look forward to hearing from you.